| by Earl Kong
The saving of human life will take precedence over all other management
as the Park Service strives to protect human life and provide for injury
free visits.
- National Park Service
Camps with standing trees have a special responsibility - the management
of those trees in the interest of the visitors, guests, and staff. Trees
are an integral part of any camp, but like any other living thing, they
require maintenance. As the number of visits around and under them increases,
the chance of an accident increases. Attitudes of camp directors about
tree maintenance are separated into two groups, those who have had an
accident, or near miss, and those who have not.
A camp's staff that has never experienced a hazard tree accident usually
makes statements such as - "That tree has been there for many years and
it hasn't failed yet." "Hazard trees are an acceptable risk." "The board
doesn't want anything done to the trees." "We don't want to change the
looks of the camp." Or, "We don't have time."
Camp staff that have had a hazard tree event usually makes statements
such as - "Go through camp and take care of every defective tree, we
don't want any more accidents!" "One more accident, and parents won't
send their kids here." And "We can plant other trees!"
Camps usually have well thought out safety plans for wet floors, insects,
vehicles, water, sunburn, food, equipment, etc., but, regarding trees,
there is usually a sense that not much can be done, that chances of hazard
tree accidents are remote enough to be an acceptable risk, or the love
of trees outweighs the hazards.
Trees fail and branches fall on a regular basis across trails and use
areas. Maintenance staff ordinarily clean up the litter, and it's back
to life as usual. When failed trees damage cabins and other structures,
maintenance staff clean up and repair buildings . . . and life in camp
goes on, with possibly some discussion about what could have happened
if someone was there at the time.
This attitude was acceptable when not much information was available
about what makes a tree fail or what factors precondition a tree to fail.
The science has always existed, but some outdoor recreation organizations
have not had access to the information about tree defects. The forest
products industry, government agencies, and research organizations have
information readily available for the general public and outdoor recreation
enthusiasts. Responsible camp managers now have the tools necessary to
identify and rectify hazardous tree situations in their camps. The results
should be safer camps.
Hazard Trees
Most hazard tree accidents occur during storms. Storms do serve an important
task. They "mop-up" hazards created by previous storms, but they also
create new hazards. They remove weak trees and/or branches during a predictable
time - the storm event. They also create additional hazards as well as
weakened situations that may or may not wait for the next storm. Depending
on the severity of the wound or break, a slight breeze may be all that
is necessary to cause failure. Some of these failures occur during perfectly
calm weather. Branches over a trail that are broken and being suspended
by other branches - called "widow-makers" by woods-workers - are the
most common of these. Trees leaning, with decay in their root systems,
are a definite risk for unpredictable failure. In cases where there is
decay, failure is on a definite schedule based on the weight of the hazard,
the speed of the decay, and, of course, weather.
Stability Factors
A tree's failure is seldom caused by one factor. Because there are so
many factors affecting a tree's stability, there is always a level of
uncertainty as to if, how, or when it will fail. There is certainty,
however, that defective trees have a higher potential for failure than
normal trees. Uncertainty is presented by the following variables:
- Weather - wind, snow, ice, and rain at different levels and combinations.
- A tree's characteristics - species, age, height, crown, sail, health,
arrangement, and degree of lean.
- Pathogens - tree infections (Sometimes pathogens are hidden within
the tree, or they may be very visible. Pathogens accelerate a tree's
hazard potential.)
- Soils - the soil's structural makeup and the amount of moisture
it is holding (e.g., rainwater lubricates soil, reducing its capacity
to anchor a tree's roots).
There is often uncertainty about how or when a tree will fail, but we
should not use this as an excuse to avoid treating the situation. If
we know that an unsafe tree exists, it is irresponsible to leave its
failure to chance.
Rating Systems
A rating system is a good tool for managing hazard trees. It can alert
us to potential problems and give us an idea as to the level of weakness
or strength of a tree based upon its structure. A rating system is not
infallible, but it can help predict a tree's potential for failure. Tree
failure usually involves a combination of factors that do not necessarily
present themselves in a predictable succession of events.
Besides alerting us, rating systems are good for recording data on trees
with defects and for plotting the progression of such defects, but, more
considerations are necessary for an effective management program. Good
hazard tree management is to conduct a comprehensive analysis of the
trees and their environment.
A Practical Program
A practical hazard tree management program recognizes three basic categories,
or levels, of trees.
- Level One - trees that offer a clear and present threat; they can
fail on their own.
- Level Two - trees that are defective, but those defects are not
significant enough to present an imminent threat.
- Level Three - trees that are normal in health and structure.
All level one trees should be abated. All level two trees should be
managed. A level two tree's defects should be analyzed, its potential
targets should be determined, and choices should be weighed. Level three
trees should be protected and managed in such a way as to keep them healthy
and free from defects. The principle behind a hazard tree program is
to first identify and remove those hazards that offer a clear, immediate
threat, and then to create a management plan for the other trees.
Hazard Tree Management Plan
A good hazard tree management plan should be established by a professional
or the most qualified people the organization has available. In some
cases, a professional can train the staff, who then can write and manage
the plan. The plan should start with goals and objectives, then field
evaluations, and succeeding treatments, if necessary. The plan should
be written with good records of activities and dates. Follow-up evaluations
should be done on a routine basis, at least annually, as well as after
all storms. A map of the facility is a necessary tool. It can specifically
identify and record problem areas. Any tree within striking distance
of a use area should be analyzed. The Hazard Tree Handbook, can be used
as a guide (see the Resources at the end of this article).
Evaluations
Evaluations in areas with few trees can be done with a single survey. Evaluations
in areas with a large amount of trees should be done in two phases. The first
phase is to identify level-one hazards only. After those hazards are identified
and treated, then a second survey is conducted to identify the level-two
hazards. These trees will require the most considerations.
Decisions have to be made as to whether to remove, modify, monitor,
or avoid. Specific evaluations should be made as to why the tree is less
than normal, what the potential damage is, and what action is taken to
prevent this potential failure or damage from occurring. Consider the
following when conducting evaluations: dead trees; uncharacteristically
leaning trees; dead branches; disease and/or damage to the roots, bole,
and crown; mushroom-like growth anywhere on a tree; cavities and holes;
thinning foliage; cracks and splits; oversized limbs; and dead or broken
branches on the ground.
After level-one hazards are removed, proper evaluations, considerations,
decisions, and planning for the remaining trees can begin. The level
three, or normal, healthy trees should be evaluated for whatever outside
factors can affect them (e.g., fire, disease, other trees, and damage
from people and their various activities). Protective measures to preserve
these trees should be considered.
Considerations
The age of the tree is a very important factor. As an example: During the 1920s
and 1930s most of western Washington State was logged for its timber. About
a third of this logged area naturally regenerated to Red Alder. The lifespan
of Red Alder is sixty to eighty years. Today in the year 2002, there are
many camps functioning among these over mature, dying, and dead trees, and
accidents are happening. Some camp staff prudently treat the situation, and
some feel that no action is necessary.
It is important to know the age of the trees in your camp and the expected
lifespan of these species. As trees approach maturity, branches start
to die and fall, the root systems begin to fail, disease has had a chance
to wreak havoc and earlier defects are now poised for failure.
Adjacent trees can present information about any tree under consideration.
Some diseases spread from tree to tree. Insects attacking certain trees
can move to other trees. Activities, such as roads, trail, and campsite
construction and maintenance, can damage trees - particularly the roots
and lower bole. It is almost a sure thing that one pathogen or the other
will infect any exposed wound, resulting in a progressively weaker tree.
Treatment
Treating hazardous trees involves choices. The first choice is whether to treat
the hazard or to remove the threatened activity. For example, a trail passes
under a tree deemed hazardous, but the tree has significant meaning to the
organization. The choices are to either remove the tree or to reroute the
trail beyond the striking distance of the hazard. A tree can be honored from
a short distance.
Other than removing a tree in its entirety, the remaining choices are
pruning to remove certain branches or limbs or topping to remove an upper
portion of the tree. The reasons for pruning are to remove dead, diseased,
or otherwise hazardous material and to reduce the sail (the wind catching
ability). Topping can reduce the striking distance as well as the sail.
Good forest management should be an integral part of any hazard tree
program. The primary goals of most forest management plans are to grow
healthy, thrifty trees and also to remove the defective, diseased trees
- replacing them with healthy vigorous ones. A hazard tree plan has similar
goals. It promotes healthy trees, removes the defective, hazardous trees,
and replaces them with healthy nonthreatening trees.
Balance can be reached regarding the aesthetic value of trees and the
potential damage or pain that they can cause. The dilemma for managing
trees in a camp usually involves the role of trees in the presentation
of the camp versus the responsibility a camp has regarding safety. Invited
guests have a right to expect that the organization has made the camp
safe for their visit.
Originally published in the 2002 September/October
issue of Camping Magazine. |
